1. Field of the Invention
The present invention relates to torque sensors and more specifically to a torque sensor, of the type which can detect the torque applied to a rotating body or the like, without direct connection or contact therewith and which type of sensor makes use of the so called magnetostriction phenomenon.
2. Description of the Prior Art
JP-A-61-127952 and JP-A-61-127953 disclose previously proposed torque sensors of the type which are front of contact with the rotating body in which the torque is being measured. In these prior art arrangements, one or more sensor elements are disposed about the rotating body in a transmission case and secured to rib flanges or the like of the casing by way of screws or the like.
These sensor arrangements are arranged to project from their mounting sites and juxtapose the peripheral outer surface of the shaft in which torque is to be sensed and to include U shape cores on which exciting and measuring coils are wound.
However, these devices have suffered from the drawback that as they are exposed to only a portion of the rotating shafts they tend to be subject to "eccentricity" noise which is generated when the shaft is subject to the application of torque which induces twisting deformation and causes the portion of the shaft to which the sensor is exposed to become momentarily eccentric.
A further drawback comes in that the voltage output signal of the device is relatively low. To overcome this it is necessary to increase the number of windings on the sensing and exciting coils. However, this measure results in the size of the sensor being unacceptably increased to the point wherein disposal in the confines of a transmission case becomes very difficult.